Though I do try to stay out of the OOC comments for the sake of good RP, when I leave the game I do have a tendency to say goodbye once via an OOC instead of sending the five or six individual tells depending upon which of my friends happen to be playing at that moment. When it is just Lushen and I, then I do it via TELL since it is just one entry. (yes, we are a group of RL friends who play together ... six of us all together)
I hope you wouldn't consider this 'getting old to hear'

I will agree though that whether in party mode or not ... //12k to level ... should be a tell and left away from OOC all together.
I think there can be a few circumstances where OOC can be tolerated ... asking a question of clarification that is not directed towards a particular person thus being asked of the group to me is okay. Why ask the same question over and over in various tells especially if it might be pertinent.
OOCs down to Zero ... not likely ... but minimizing the OOCs to essentials is very do-able. I'm not sure about the rest of you, but having played pnp type games for many years, OOC questions happen in any type of RPing world.